Scarfing apparatus



March 9, 1965 v. F. NOLE ETAL 3,172,331

SCARFING APPARATUS Filed Aug. 26, 1963 2 Sheets-Sheet 1 Q O O is r 1 l6 K16 lZ a INVENTORS v 1 VITOFNOLE g M BY JOSEPH IPED N 60 ATTORNEYS March 9, 1965 v. F. NOLE ETAL 3,172,331

SCARFING APPARATUS Filed Aug. 26, 1963 2 Sheets-Sheet 2 jig .2

INVENTOR VITO I? NoLa Jose/=14 JPEDANz-L MyM f4 6/ A T T ORNE VS United States Patent 3,172,331 I SCARFiNG APPARATUS Vito F. Nole, Waterbury, and Joseph J. Pedane, Watertown, Conn, assignors to Chase Brass & Copper (30.,

Incorporated, Waterbury, Conn, a corporation of Connecticut Filed Aug. 26, 1963, Ser. No. 304,541 8 Claims. (Cl. 90-24) The invention relates to metal processing and, more particularly, to apparatus for conditioning the edges of relatively thin gauge metal strip. Primary application of the invention lies in the proper edge preparation of thin copper strip such as that used in winding transformer and magnet coils, where the thickness of the copper strip may run as heavy as 0.080" to 0.090" but usually is between about 0.010 and 0.040". However, the samp principles of the invention appear applicable for conditioning the edges of other metal strip for other applications.

The condition of the edges of metal strip used as conductors of electric current is of importance in many instances. Metal strip used in the winding of transformer and magnet coils should be substantially burr free, at least to the extent that there are no burrs extending generally transverse to the face of the metal, in order to reduce as much as possible potential low breakdown voltage points in the transformer winding. Customarily, the turns of the conducting coil metal are insulated from one another by interleaving a paperinsulator therebetween or by coating the strip with athin continuous film of insulating varnish. Such burrs, regardless of the means of insulation employed frequently either cut through the insulating medium, or present areas of low dielectric strength, and thereby lower or impair the electrical integrityv of the coil.

Conventional methods of slitting copper sheet into strips of a width useful for transformer windings produce edges which are burred to a greater or lesser extent. As the metal is cut to desired Width by the slitter, the relatively soft copper is usually distorted by the formation of a rolled torn edge, which may be slight or marked, depending upon the adjustment and the physical condition of the slitter. Various attempts have been made to produce so-called burr-free copper strip. For example, processing schedules have been devised in which the copper, in an unannealed state, is slit to desired width at thicknesses about to 40% above the desired finished gauge and then rolled to the desired final thickness. Such a schedule produces material free of burrs at the edges perpendicular to the face of the strip, but frequently the edges are rough and sharp.

Edge rolling has been tried at sufiiciently heavy gauges (about 0.010 and thicker) in another attempt to produce burr-free copper strip. Edge rolling is effective in removing burrs and in forming a rounded contour at the edge portions of the strip. However, it is extremely difficult to edge roll thin wide strip much below 0.010"

gauge as the metal tends to buckle and distort under the force exerted by the edge rollers. In addition to being limited in the gauges and widths which can be handled, this method also has the drawback of producing an edge which, although burr-free, is frequently still quite rough.

Still other attempts to produce burr-free copper strip have included the use of deburring rolls. Such rolls are mushrooms, creating burrs.

based on the concept of deforming, i.e. depressing, the metal lip created by the slitter knives. These rolls frequently produce rough, sharp strip edges also.

Sandblasting has been used but with unsatisfactory results as the metal is distorted by the sand and the edge A further objection to this method is the necessity for masking the faces of the strip to prevent damage to the flat surfaces thereof.

Etching, using either chemical or electrochemical means, has also been tried. Although these methods produce edges of desired contours, they are economically impractical because of the relatively slow processing rates attainable and cost of the equipment involved.

File boards have also been tried but have not been sat-- methods, there has heretofore been no completely satisfactory method of deburring the edge portions of copper strip. The object of the present invention, therefore, is to overcome this problem by providing simple, rapid and economical apparatus for forming smooth, rounded edges on metal strip.

Briefly, and in general, the invention comprises pulling the edges of the strip through a pair of opposed cutting tools that have a special cutting edge configuration. The cutting tools are shaped so as to produce a rounded contour on the edges of the strip, and the contouring of the edges of the strip in this manner is called scarfing. The term scarfing is used hereinafter in that sense throughout the specification.

Efiicient operation of the scarfing unit requires that the metal strip be pulled through the cutters at a steady rate of speed. Although the operation may be carried on at speeds very much higher, it is preferred to draw the copper strip through the specially contoured cutters at a speed of between 200 and 300 feet per minute At metal speeds above 300 feet per minute excessive heating of the cutters occurs and decreases their life. A coolant may be used to advantage in such cases to increase strip speed if desired.

The cutters are formed from small cutter blades of carbide type such as tungsten carbide and are notched in one side so as to form the cutting edge. Each cutting notch is generally U-shape-in configuration with tapering sides and a rounded bottom. In forming the cutting notch it has been found .that certain relationships in the dimensionsthereof are critical and must be observed in order to, obtain satisfactory results. These special relationships involve the degree of taper at the sides of the notch, as well as the value of the radius at the bottom of the notch. v i

It has been found that tapered sides for the notch are necessary. Attempts to employ blades having straight sided cutting notches have proved unsatisfactory. Moreover, the degree of taper ofthe sides of the notch must fall between the limits of 3 and 6, measured with respect to a reference line normal to the edge of the cutter blade onto which the cutting notch opens. At the same time the radius of the curvature of the notch at the 3 bottom must be equal to one-half the gauge thickness of the metal strip being scarfed, less a constant that has been determined experimentally.

Observance of these relationships has made it possible to produce copper strip with smoothly rounded, burrfree edge portions. Because of the improved edge contours of such strip, adequate edge coating of the strip edges by the application of film coatings 'ofinsulating varnish has been greatly facilitated. Experience indicates that any significant departure from these relationships results in an unsatisfactory edge condition.

While other dimensional relationships of the cutter blade and its position with respect to the work are not as important as the factors discussed above, nevertheless, best results are obtained if these relationships are kept within certain limits. Thus, while the depth of the cutting notch is not restricted to any particular value, it must be sufiicient to prevent the strip from leaving the cutter notch during the scarfing operation. An arbitrary depth of around 0.050" serves well for most'purposes, but for the thicker gauge material the depth may have to be increased to around 0.100". The cutting angle of the blades is also important, that is, the angle which the plane of the blade makes to the edge of the strip. It

has been found that best results are obtained when the cutting blades are arranged at a negative angle of between 30 and 50 with respect to the edge of the strip, or in other words the blades trail the strip at an included angle of this value. In order to accommodate sidewise movement or drift of the strip as it passes by the cutters, the cutter blades are mounted on arms which permit the blades to move laterally with the strip edges. Oppositely disposed blades are interconnectedunder spring or similar tensioning means which constantly urges the cutters into engagement with the metal strip. The amount of tension applied to the cutters, in general, is a function of strip thickness. As the gauge increases so also should the tension. Should too little tension be applied the scarfed edges will not be rounded. If too much tension is applied excessive blade wear will result and the chances of producing burrs and chatter marks will be greatly increased.

Reference will now be had to the accompanying drawings fora more detailed description of the invention.

Of the drawings:

FIG. 1 is a plan view of the scarfing apparatus showing a section of metal strip being pulled between two pairs of cuting tools;

FIG. 2 is a partial sectional view taken along the line 2-2 in FIG. 1 looking in the direction of the arrows;

FIG. 3 is a plan View of a scarfing blade;

FIG. 4 is a side elevational view of the blade shown in FIG. 3; 1

FIG. 5 is a partial plan view showing the angular relationship between the scarfing blades and the metal strip being scarfed; and

FIG. 6 is a greatly enlarged view showing the configuration of geometry of the scarfing notch in the blade.

Apparatus for carrying out the invention is. shown in FIG. 1 and comprises a horizontally disposed flat bed or base plate 10 on which there is mounted the supporting structure for the cutting tools and the means for guiding the metal strip 12 as it passes between the .cutters. Movement of the strip 12 is effected by a driving roller (not shown) so arranged as to pull the, metal in the longitudinal direction indicated by the arrow 14'. The speed of they metal strippast the cutters may be as. high 7 as 600 feet per minute but it is preferred. to keep the speedwithin the range of from about 200 to 300'feet per minute.

Two adjustable, guides 16, 16 for-the metal strip 12.

20 formed in the base plate 10. A hearing strip 22 of felt or plastic base material is mounted on the inner edge of each block 18 and engages the adjacent edge of the metal strip 12. The guides 16, 16 are adjusted so as to be spaced approximately the width of the strip 12 being contoured and so serve to limit lateral drift of the strip during the scarfing operation.

Horizontal supports 24, 24 for the strip are provided between the guide blocks 18, 18. In the apparatus shown in the drawing, three such horizontal supports are employed. The supports comprises vertical towers 26, 26 to which are joined a pair of horizontally disposed bars 28, 28. The horizontal bars 28, 28 are vertically spaced from each other so as to accommodate upper and lower alignment plates 30, 31 (see FIG. 2) which extend between the bars 28, 28 and from one set of guides 24, 24 to another. Disposed between the alignment plates 30, 31 are upper and lower liners 32, 33 that are preferably made from a compressible material such as felt, plastic, sponge rubber or the like.

In securing the proper horizontal alignment of the metal strip 12, the lower aligning plate 30 and compressible liner 32 are placed under the strip 12 while the upper aligning plate 31 and liner 33 are placed on top of the strip. The rigidity of the plates 30, 31 prevents any serious deflections of the strip 12 from the proper horizontal plane While the compressible liners 32, 33 prevent any binding between the strip 12 and the plates 30, 31.

The liners of the horizontal guides also serve to wipe the:

tions of the metal strip can be achieved with a single set' of cutters. Transverse dovetail slots 36, 36 are formed in the base plate 10 for each set and a pair of tool blocks 38, 38 are located in each slot. The blocks 38, 38 are laterally movable within the slots 36, 36 so as to be adjustable relative to the edges of the metal strip 12. Proper positioning of the blocks 38, 38 in the dovetail slots is maintained by locking screws 40, 40 in the blocks 38, 38.

Mounted at the inward end of each tool block 38 is a.

vertical tool post. The tool posts comprise bolts 44, 44

that are screwed into threaded openings in the tool blocks 38, 38 so as to provide a height adjustment for the cutting tools. The height of the tool posts 44, 44 and hence the cutting tools, is fixed by tightening the threaded lock rings 46, 46 against the tool blocks.

Each tool post 44 has a tool arm 47 formed by a pair of spaced horizontal plates 48, 48 that are fixed to a cylindrical sleeve 50. The cylindrical sleeve 50 is mounted on bearings carried by the tool post 44 so that the tool arm 47 is free to rotate around the post 44.- At their outer ends the plates 48', 48 terminate in a vertically disposed plate 49 which is secured in any suitable fashion to a similar plate 51. Plate 51 has secured to it a pair of generally triangular spaced horizontal plates 53, 53 which,

together with the plate 51,. serve as an extension of the:

tool. arm 47. V

The scarfing blades 52, 52 are mounted on the tool arm 47 by securing each blade to a tool. holder 54' mountedat the free end of the extension of the tool arm 47. Securement of the blade to the holder 54 is effected by a pair of lugs 56, 56 which clamp the blade 52 to the holder 54 when the holding screws 57, 57 therefore are tightened.

The tool holder 54 may comprise a metal block 58 vertically disposed between the upper and'lower plates 53, 53' of the tool arm 47. A bolt 60 passes through the plates 53, 53and the block 58 to lock the block in fixed position to the tool arm 47. Adjustment of the tool holder 54" relative to the tool arm 47 may be effected by backing off theznut'62for the. bolt 60 to free the block 58 for pivotable= movement therearound. A spring 64 is mounted between the bolts 60, 60 of each pair of oppositely disposed tool arms 47 so as to constantly urge the cutters toward engagement with the edge of the metal strip 12.

The scarfing blades 52, 52 are preferably formed from tungsten carbide and may be generally rectangular in shape. A notch 66 is ground into one edge portion 68 of the blade and serves as the cutting edge therefor. As shown in FIG. 4 the cutter blade 52 is formed with raked sides 70, 70 and the notch 66 is ground at a similar angle. The general working position for the blade 52 is shown in FIG. 5 wherein the blade holding parts have been omitted for the sake of clarity. To obtain the best results from the cutter the angle indicated at 72 which the blade 52 makes with the edge of the metal strip 12 should be within the range of from 30 to 50. The cutting angle here is negative, i.e. the blade is in trailing relation to the strip travel, as indicated by the direction arrow in FIG. 5.

It has been found that a certain configuration and proper dimensioning of the notch 66 are necessary if satisfactory scarfing of the metal strip 12 is to be obtained. This is shown in detail in FIG. 6. The configuration of the notch 66 is generally U-shaped with tapered sides 74, 74 and a rounded or radiused bottom 76. While the degree of taper is constant regardless of the gauge of the metal strip 12 being processed the radius at the bottom '76 of the notch 66 is directly related to the metal thickness of the strip being scarfed. It is necessary, therefore, to use different cutter blades 52 for different gauges of the metal strip 12 being scarfed. For all cutters the degree of taper of the sides 74, 74 of the notch 66 must be between 3 and 6 as measured with respect to a reference line normal to the edge 68 of the cutter blade 52. This measurement is indicated by angle A in the accompanying drawings. The tapered sides 74, 74 extend tangentially outwardly from the base 76 of the notch and the radius at the bottom should be kept to a value falling within the range expressed by the equation:

where R is the radius in inches of curvature at the bottom 76, t is the thickness in inches of the strip 12 being scarfed and k is a constant experimentally determined as being about .001. Experience has shown that only slight variation from the above formula will result in unsatisfactory edges. Burrs appear on the material when the thickness thereof decreases more than about 0.001 from the design gauge of the particular cutter in use. This is well within the limit of commercial tolerances maintained in strip metal fabrication.

The depth of the notch 66 (indicated by the arrows 73, 78) is not as important as the tapering of the sides 74, 74 and the proper curvature of the bottom 76, and may be varied as desired provided the notch is deep enough to prevent dislodgement of the notch from the edge of the metal strip. For the smaller gauges (below 0.013") the depth of the notch 66 may advantageously be about 0.030" while for thicker gauges (0.013 to 0.041") the depth of the notch 66 may be from about 0.040 to about 0.050. For heavier gauge material up to around 0.080" to 0.090", a depth of 0.100" is satisfactory.

Following the teachings of the invention, applicants have been able successfully to scarf copper strip ranging in thickness from 0.009 to as much as 0.080" or slightly more. In each case the contoured edge was free of burrs and smoothly rounded. The following table provides typical notch dimensions found to produce successful edge scarfing on a number of different strip gauges:

Metal Radius of Angle of Depth of Gauge, Bottom, Taper Notch,

inches inches inches Other strip thicknesses, both greater and smaller, would appear to be equally capable of successful edge scarfing in accordance with the teaching herein, but the foregoing are representative of thicknesses which are practical and economical for most current applications.

What is claimed is:

1. Apparatus for conditioning the edges of metal strip, said apparatus comprising at least one edge scarfing blade mounted for engagement with an edge portion of said metal strip, said scarfing blade having formed therein a substantially U-shaped cutting notch having tapered sides and a curved bottom, and means for moving said strip past said scarfing blade while said blade is disposed at a negative cutting angle relative to the direction of strip travel.

2. Apparatus as set forth in claim 1, wherein the sides of the scarfing notch in the scarfing blade are tapered at an angle of between 3 and 6 measured with respect to a reference line normal to the edge of the blade onto which said notch opens.

3. Apparatus as set forth in claim 2, wherein the radius at the base of the scarfing notch is determined by the formula where R is the radius in inches and t is the thickness of metal in inches to be edge scarfed.

4. Apparatus as set forth in claim 3, wherein said edge scarfers are disposed at a negative scarfing angle of between 30 and 50 with respect to the edge of the strip.

5. Apparatus as set forth in claim 4, wherein means are provided for maintaining the strip substantially in the plane of the scarfing notch in the edge scarfer as the strip passes therethrough.

6. Apparatus as set forth in claim 5, wherein said apparatus has a pair of edge scarfers disposed at opposite sides of the strip and means for constantly urging said scarfers into engagement with the strip.

7. Apparatus as set forth in claim 6, wherein said oppositely disposed edge scarfers are urged into contact with the edges of the strip by spring means connecting said edge scarfers.

8. Apparatus as set forth in claim 7, wherein said edge scarfers each comprise a blade having a cutting notch formed therein and said blade is adjustably mounted on a tool arm, said tool arm being pivotably mounted with respect to the metal strip.

References Cited by the Examiner UNITED STATES PATENTS 1,292,157 1/ 19 Townsend. 1,958,147 5/ 34 Kelley et al. 2,508,534 5/50 Paxson -24 WILLIAM W. DYER, 111., Primary Examiner. 

1. APPARATUS FOR CONDITIONING THE EDGES OF METAL STRIP, SAID APPARATUS COMPRISING AT LEAST ONE EDGE SCARFING BLADE MOUNTED FOR ENGAGEMENT WITH AN EDGE PORTION OF SAID METAL STRIP, SAID SCARFING BLADE HAVING FORMED THEREIN A SUBSTANTIALLY U-SHAPED CUTTING NOTCH HAVING TAPERED SIDES AND A CURVED BOTTOM, AND MEANS FOR MOVING SAID STRIP PAST SAID SCARFING BLADE WHILE SAID BLADE IS DISPOSED AT A NEGATIVE CUTTING ANGLE RELATIVE TO THE DIRECTION OF STRIP TRAVEL.
 2. APPARATUS AS SET FORTH IN CLAIM 1, WHEREIN THE SIDES OF THE SCARFING NOTCH IN THE SCARFING BLADE ARE TAPERED AT AN ANGLE OF BETWEEN 3* AND 6* MEASURED WITH RESPECT TO A REFERENCE LINE NORMAL TO THE EDGE OF THE BLADE ONTO WHICH SAID NOTCH OPENS. 